Creative Research Enterprises

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DIMER PHOTOCHEMISTRY IN THE PALEOATMOSPHERE

• E. C. Zipf
• University of Pittsburgh
• (Edczipf_at_aol.com)
• Sheo S. Prasad
• Creative Research Enterprises
• (ssp_at_creativeResearch.org)

• Dimer Photochemistry may have been very
  important in the prebiological paleoatmosphere
  before the advent of the biological
  photosynthesis
• May have influenced the evolution of the
  primitive marine life and also of the O3 layer
  during the time period when the O2 layer was
  developing

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DIMER PHOTOCHEMISTRY WAS IMPORTANT DUE TO LOW
ATMOSPHERIC TEMPERATURES
Illustration for the era of O2 level 10-4
present
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IN O2-DEFICIENT PALEOATMOSPHERE DIMER
PHOTOCHEMISTRY MAY HAVE DONE THINGS NOT POSSIBLE
IN THE PRESENT ATMOSPHERE

• With O2 being at 10-5 to 10-3 PAL (Present
  Atmospheric Level), the chemically significant
  UV penetrated the region where dimer population
  is appreciable.

Flux at the ground for various O2 levels
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NOX PRODUCTION AN EXAMPLE OF IMPORTANT ROLE OF
DIMER PHOTOCHEMISTRY IN PALEOATMOSPHERE

• O2N2 hv (?200-250 nm) ? NO NO
• Laboratory experiments put wavelength averaged
  quantum yield (?) at ? ? 3.3 x 10-2 NO /photon
• Also dimerization might facilitate the spin
  forbidden absorption of these photons by O2 of
  the O2N2 dimer
• N NO2 as the primary products are ignored
  since N NO2 ? N2O O

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TOTAL NOX PRODUCTION RATE WAS SUBSTANTIAL

• Assuming ?-averaged ? was valid for each
  wavelength bin
• Note, the total NOX production rate was
  considerable at even the ground level

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LET US PUT THE DIMER NOX PRODUCTION IN A PROPER
PERSPECTIVE

• The N2O O(1D) ? NO NO was insignificant due to
  deep penetration of the UV
• Lightning is thought to be the only important
  source of NOX in the post-bolide impact era
• The dimer source, however, may have been 50 to
  100 times larger than the lightning source
• The dimer was thus the most important NOX source
  in the post-bolide prebiological paleoatmosphere

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THIS DIMER CHEMISTRY MAY HAVE AFFECTED THE
EVOLUTION OF LIFE IN OCEAN AND LAND

• Since it was a global tropospheric source, it was
  particularly effective in providing nutrients to
  marine life in the post-bolide impact era
• It may have created a low-altitude
  paleoionosphere that modified the electrical
  properties of the Precambrian atmosphere.
• It may have influenced the pace of formation of
  the O3 shield over the biosphere when the O2 was
  growing from its prebiological level to the
  present level

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CONCLUDING REMARKS

• The dimer photochemistry may have been quite
  important in the prebiological paleoatmosphere
• It is therefore hoped that this presentation will
  motivate the key measurements- the wavelength
  dependence of the quantum yield